In a case of commonly-used bagging packaging machines, empty bags stored in a magazine serving as an empty bag storage unit are positioned properly by keeping the empty bags' mouth edges in contact with a stopper, for example, and the positioned empty bags are extracted from the magazine one by one and supplied to grippers. The supply of the empty bags to the grippers is performed by having the grippers directly pinch each empty bag in the magazine or by transferring each empty bag in the magazine to the grippers while suction holding it so as to hand over it to the grippers, for example. Each empty bag supplied to the grippers is transferred in the state of being gripped by the grippers. During the transfer, various types of prescribed packaging processes are performed successively, such as the printing of information like the best-before date, the opening of the bag mouth, the loading of the bag with the contents to be packaged, and the sealing of the bag mouth.
However, when the empty bags are relatively thin and soft and lack stiffness, there are cases where the bag mouths placed in contact with the stopper bend or fold during the positioning of the empty bags and the bend/fold causes a positioning failure (see FIG. 6 of Japanese patent application publication No. 2006-036325, for example).
Further, when the surface of the bag is made of a relatively slippery material, there are cases where the bag is displaced in its lengthwise direction when the empty bag is supplied to the grippers or when the empty bag gripped by the grippers is loaded with the contents to be packaged. Furthermore, similar problems may arise in cases where the contents to be packaged contain oil or the like and the contents adhere to empty bag holding surfaces of an empty bag supply device or gripping surfaces of the grippers.
As explained above, when the positioning or the supply of the bag is not performed appropriately or when the gripping of the bag by the grippers is not performed appropriately, the empty bag is gripped by the grippers in a condition deviated from the original arrangement. If the sealing process is performed on the mouth of the bag in such a condition, the position of the seal formed at the bag mouth deviates from the original position. Such a packaging bag with a deviated seal position is not only inferior in appearance but can also be handled as a defective packaging bag (see FIG. 4 of Japanese Utility Model Registration No. 2578608, for example).
In consideration of such a situation, Japanese Utility Model Registration No. 2578608 discloses a bag gripping position detection device that detects the position of the bag relative to the grippers by using a sensor. If the bag is gripped by the grippers in a condition deviated from a prescribed position, the bag gripping position detection device skips the subsequent packaging processes (e.g., the contents loading process, the bag mouth sealing process, etc.) and ejects the bag in the empty state to the outside of the machine. With the bag gripping position detection device, the occurrence of defective packaging bags can be reduced, and further, the empty bag ejected to the outside of the machine can be reused by setting the empty bag in the packaging machine again.